JP2001111522A - Method and device for data allocation in duplicative communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system to be dynamically constructed, so as to use a part or the entire part of band width of a communication channel. SOLUTION: This method is for allocating data to be transmitted on a communication channel, detects characteristics of the communication channel and allocates the data so that data transmission is constructed on the communication channel in one of a first mode, in which the data is transmitted in a frequency area in which upstream data transmission and downstream data transmission are not substantially duplicated and a second mode in which the data is transmitted in a frequency area, in which the upstream data transmission and the downstream data transmission are substantially duplicated by using the characteristics of the communication channel in a processing unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to communication systems and, more particularly, to overlap-enable.
d) a method and apparatus for use in a communication system.

[0002]

BACKGROUND OF THE INVENTION In order to spread high data rate interactive services, such as video conferencing and Internet access, to more home and small business users, high speed data communication paths are required. Fiber optic cables are designed for such high data rate
Although a preferred transmission medium for services, it is not readily available on existing networks and the cost of installing fiber optic cables is enormous. The current telephone wiring connection consisting of twisted pair media is video on demand (video o
It is not designed to support interactive services such as n demand, or the high data rates required for even high-speed interconnects. Accordingly, in order to improve transmission capacity within the fixed bandwidth of existing twisted pair connections, ADSL (Asymmetrical Digital Subscrib
(er Line) technology has been developed to enable interactive services to be provided without having to lay new optical fiber cables.

[0003] DMT (Discrete Multi-Toned) is a multi-car which divides the effective bandwidth of a communication channel such as a twisted pair connection into a number of frequency sub-channels.
rier) technology. These sub-channels are also referred to as frequency bins or carriers.
DMT technology is ANSIT1 for ADSL system.
It has been adopted by the E1.4 (ADSL) committee.
In ADSL, DMT is 2 kHz from 26 kHz to 1.1 MHz for downstream transmission for end users.
Generate 50 individual 4.3125 kHz subchannels and 2 for upstream by end users
It is used to generate 25 sub-channels from 6 kHz to 138 kHz. Each bin is assigned the number of bits to be transmitted in each transmission. The number of bits allocated to the ADSL system is 0 and 2 to 15 bits.

Prior to transmitting real-time data in an ADSL system, an initialization process is performed. In the first part of the initialization process, activation and acknowledgment steps are performed. After power-up of the ADSL system, the transmission activation tone (transmi
It is during this step that the (t activation tone) is generated. Transceiver training
ining) is the next step in the initialization process. During transceiver training, the equalization filters of the ADSL system are trained and system synchronization is established. Then, as part of the initialization process, channel analysis and exchange
d exchange) is performed. During channel analysis and exchange, the signal-to-noise ratio (SNR) of the channel
e Ratio) is determined and the bit loading of the bin
Configuration and other configuration information is transferred.

[0005] Following the initialization process, a real-time
Data transmission starts. During real-time data transmission, the configuration proposed by the ANSI standard requires that each carrier be transmitted at a nominal amount of power. Since only minor power gain adjustment changes occur between carriers, the nominal power (n
The ominal amount of power is proposed to be the same full power in all bins. However, assigning a nominal amount of transmitted power to each carrier has drawbacks. For example, one problem is that allocating a nominal amount of power to a carrier that is not transmitting data results in unnecessary power consumption. This is the maximum data rate that the requested data rate can achieve on the line.
Occurs when the rate is lower than the rate. Additional power results in additional system costs in terms of power consumption. Another problem with transmitting power on unused bins is that if the carrier signal is attenuated over long line distances, data may not be transmitted with the desired reliability. When this occurs, the bit allocation capacity of the bad bin is set to zero, but in the proposed standard configuration, its transmit power remains allocated to the new unused bin. Thus, even without high data rates, there is a high cost in terms of power. Another problem with the ADSL standard is that crosstalk interference occurs when signals are transmitted on adjacent lines at similar frequencies.

[0006]

Generally, a typical DM
More than half of the power consumed by the T system is consumed by line drivers. In addition to the thermal problems associated with increased power, there is the additional problem that crosstalk from adjacent telephone lines can increase line noise levels by as much as 40 dB. Therefore, it would be advantageous to optimize the power consumption of a DMT and reduce crosstalk between adjacent twisted pair wires.

[0007] In addition, many communication systems, such as ADSL systems, use the frequency overlapped re- sults available through the uplink and downlink.
gion). Utilizing this overlap region in certain applications can improve performance, such as improving capacity and loop length coverage. However, communicating on the overlapping area may have certain side effects such as crosstalk. Accordingly, there is a need for improved methods and apparatus for utilizing overlap-enabled communication systems.

[0008]

1 shows an ADSL system 10. FIG. AD
The SL system 10 includes a remote terminal 20 connected by a twisted pair transmission medium and a central office (central office).
e) 30. Remote terminal 20 and central office 30 are connected to system controllers 22, 34, respectively.
Consists of Further, the remote terminal 20 and the central office 30
It comprises transceivers 24 and 32, respectively. The transceiver includes a processor unit, respective filters, such as digital and analog filters, and a line driver that communicates with a communication channel. Filters and line drivers can be dynamically configured by the processing unit to enable communication over various selected frequency regions of the communication channel. ADSL system 1
0 indicates that the present invention can be implemented. In operation, the central office 30
The downstream data is transmitted to the remote terminal 20 on the transmission medium 15. The data is received at the remote terminal 20 by the transceiver 24, the transceiver 24
The received data is provided to the system controller 22 for further processing. Similarly, upstream data is
Transmitted from the remote terminal over transmission medium 15 and received by central office transceiver 32, central office transceiver 32
Supplies this data to the system controller 34.

FIG. 2 shows an SNR reference table for use in ADSL system 10. The SNR reference table indicates the SNRref value, which is the SNR required for a bin to transmit a specific number of bits at a specific bit error rate (BER). For example, according to the table of FIG. 2, a bin determined to have an SNR of 30 can transmit 7-bit data. Also, the value of the SNR reference table, if any, is the error correction (error corre
ction) depending on the type. For example, using error correction can reduce each SNRref value in FIG. 2 by three. With this reduction, a bin with an SNR of 30 can transmit 8 bits. Generally, the SNR reference table is derived empirically, but may be derived based on simulation results or theoretical results.

FIG. 3 illustrates a method for practicing the present invention. Although particular embodiments address particular DMT configurations, it should be understood that the present invention applies to any DMT configuration. In step 311, the ADSL channel is analyzed. In one embodiment of the present invention, the channel analysis step 311 returns a signal-to-noise ratio (SNR) for the initial channel. Generally, the channel analysis step 311 of FIG. 3 is performed as part of the initialization process. However, other embodiments in which the steps of FIG. 3 are performed during real-time operation are also contemplated by the present invention.

In step 312, the data capacity of each bin is calculated. In one embodiment, the data capacity is:
SNR of the carrier determined in step 311;
It is calculated based on the SNR reference table of FIG. The data capacity is, for a given SNR criteria table,
It can be obtained by specifying the maximum number of bits that can be transmitted. For example, according to the table of FIG.
The maximum number of bits that R can assign to 32 bins is 7 bits.

Next, at step 313, the carriers or bins are reordered from maximum capacity to minimum capacity. Next, in step 314, the data rates to be transmitted are allocated starting from the carrier with the largest capacity up to the carrier with the smallest capacity. Data capacity is allocated until the specified data rate is achieved.
The carrier used to transmit data at the desired data rate by first being assigned to the bin with the highest data rate (used carrier)
s)) can be minimized. Step 3
At 15, the power on the unused carrier is reduced to minimize the power used to transmit the specified amount of information. Generally, the power is reduced by an order of magnitude from the power of the used bin. This means that each channel
This is an advantage over prior art that requires maintaining a nominal amount of power, whether used or unused. Reducing power to unused bins allows for optimal power dissipation.

FIG. 4 shows another embodiment of the present invention. In step 411, a subset carrier X is specified for a set N of carriers. In general, subset X
Represents a carrier that is prioritized or avoided during the bit loading assignment process. Next, subset X is weighted. This weight may be explicit, in which case the weight may be specified by the user or implicit,
In that case, the system has a default weight for subset X. For example, subset X can be implicitly heavily weighted. The weighting function will be described with reference to step 415.

At step 412, a channel analysis is performed for each carrier of set N. Step 41
The channel analysis of step 2 of FIG.
1 is performed in the same manner as the channel analysis. Next, in step 413, the bit loading capacity is calculated for each bin in carrier set N. This step is similar to step 312 in FIG.

In step 414, the carriers of set N that are not in set X are reordered from the maximum bit loading capacity to the minimum bit loading capacity to form a sorted set of carriers. This step is functionally similar to step 313 of FIG. 3, except that it is performed on a subset of the set.

In step 419, the carriers in set X are also reordered from the maximum bit loading capacity to the minimum bit loading capacity to form another reordering set. In another embodiment, set X need not be reordered.

At step 415, bins associated with carrier subset X are inserted into or removed from the permutation set of carriers. In one embodiment, where the bins of set X are implicitly heavily weighted, the set is placed in a permutation set before or after bins that meet a predetermined condition. For example, heavily weighted bins are placed before bins with the highest capacity. In another embodiment, the heavily weighted bin may be located between a bin having 10 bits capacity and a bin having 9 bits capacity. In general, heavily weighted sets are inserted with bins having higher bit allocation capacity. 1
In one embodiment, where 5 bits are the maximum loading of the bin, the heavily weighted set is typically inserted at or above the 7-bit allocation level.

Similarly, if the bins of set X are implicitly lightly weighted, these bins can be completely excluded from the permutation list, or inserted after the bins with the least bit loading capacity, or specified. It can be inserted between bins with loading levels. In general, a lightly weighted set is inserted with bins having low bit allocation capacity. In one embodiment, where 15 bits are the maximum loading of the bin, the lightly weighted set is
Generally inserted below the 7-bit allocation level.

In embodiments where numerical weighting is applied, the exact locations of the bins in set X are placed or excluded based on the value of the weight.

In step 416, the number of bits required to support the specified data rate is assigned to the bin based on the set's reordering order.
For example, assume that set X is inserted between bins with loading capacities of 13 bits and 14 bits. The assignment has a loading capacity of 15 bits,
Start with a bin that is not in set X. When 15 bits are allocated to the first bin, it has a capacity of 15 bits,
Other bins not in set X are assigned 15 bits, and so on until all 15-bit bins are fully assigned. Next, all 14 not in set X
Bit bins are similarly filled. Next, the bins of the set X are filled, and thereafter, the bins having a capacity of 13 bits which are not in the set X are loaded. After each bin of set X has been filled, the filling process continues with the 13 bit capacity bin.

FIG. 5 shows another embodiment of the present invention that can reduce crosstalk between adjacent lines. Step 501
, A subset X1 of carriers is specified for the first line card. In step 502, the flow of FIG. 4 is applied to subset X1. This substantially minimizes the number of carriers that the line card 2 needs to drive to support a particular data rate.

In step 503, a substantially non-overlapping subset of carriers X2 is specified for the first line card. In one embodiment, sets X1 and X2 are mutually exclusive in that they attempt to allocate data capacity for bins operating at different frequencies.
In yet another embodiment, sets X1 and X2 are selected to buffer used bins on line cards separate from each other. For example, if set X1 specifies bins 1-10 as the first bin to be filled,
Set X2 is bins 12 to 2 as the first bottle to be filled.
Specify 1. To the extent that bin loading capacity can be allocated within the designated bin, there is a bin 11, which is an unused bin, buffering the frequency range of sets X1 and X2. This buffer can increase resistance to crosstalk.

Once the set X2 has been defined, the method of FIG. 4 is applied to optimize the power of the system. In step 505, data transmission takes place, allowing for optimization of power dissipation and minimizing crosstalk between adjacent lines.

FIG. 6 shows a method for allocating data in a communication system. At step 610, the remote terminal transceiver (R2) receives the requested data rate. In step 620, TR2 determines at least one mode priority and area list (mode priori
ty and region list). The data rate, mode priority and region list may be, for example, user input received by TR2, received by central office transceiver (TR1) and forwarded to TR2,
Alternatively, it may be fixed. The region list may divide the total available bandwidth of the communication channel into individual frequency subbands called regions. Examples of three areas are POTS (Plain Old Telephone System) as shown in FIG.
Area, overlapping area and non-overlapping area. The priority list contains the relative priorities of the regions. In step 630, TR1 transmits the training sequence on all carriers in multiple regions of the communication channel during the capacity measurement sequence so that TR2 can calculate the capacity of each region in step 640. The plurality of areas include, for example, overlapping areas and non-overlapping areas (eg, FDs).
M full (FDM full) region or FDM lite (FDM lite) region. Further, it may include a POTS area. At step 650, TR2 assigns the requested data to individual mode regions based on the priority list and the mode region characteristics (described below with reference to FIGS. 7, 9 and 10). At step 660,
TR2 configures itself to receive at the requested data rate, sends configuration information to TR1, and properly configures the transmitter of TR1.

FIG. 8 shows a method for allocating data in a communication system. At step 810, the remote terminal (TR2) receives the requested data rate. In step 820, TR2 receives the mode priority and region list. The data rate, mode priority and region list may be, for example, user input received by TR2, or may be received by central office transceiver (TR1) and forwarded to TR2;
Alternatively, it may be fixed. At step 830, TR
1 transmits the training sequence in multiple regions during the capacity measurement sequence so that TR2 can calculate the capacity of each region in step 840. In step 850, TR2 sets the maximum area information of each area to T
Send to R1. At step 860, TR2 receives the new requested data rate and the new priority list. In step 870, TR2 assigns the requested data to individual mode regions based on the priority list and the mode region characteristics (described below with reference to FIGS. 7, 9 and 10). Steps 810 and 820 are optional. If steps 810 and 820 are used, TR1 determines that TR2 has the capacity of each region as TR1
, Then wait until step 860 to send the first requested data rate, priority list and region list.

Referring to FIG. 9, a specific method for allocating data is shown. In this method, at step 902, characteristics of a communication channel are detected. Examples of characteristics include capacity, channel power detection, channel length, noise, terrain (geo
graphy) and user input. Next, in step 904, a data transport method or area is selected. The method or region may be an overlapping or non-overlapping method or region. Once a particular method or region is selected, at step 906, data is communicated on the channel using the selected method. By allowing different methods or regions to carry data and making decisions based on channel characteristics, communication data to be transmitted can be assigned to specific channels in a flexible and configurable manner. Furthermore, the step of selecting a particular data carrying method or region is performed dynamically, so that limited communication resources such as particular frequency bins in the ADSL system can be efficiently used.

Referring to FIG. 7, a schematic diagram illustrating the relationship between transmission power and frequency for a redundant communication system is shown.
The communication channels are the POTS area 710 and the overlap area 708
And frequency division multiplexing (FDM)
multiplexed) is divided into individual modes or frequency domains, including a full rate domain 706. These frequency domains form the full spectrum of the full rate ADSL spectrum 702. G. FIG. light spectrum 70
In the configuration of No. 4, there are a POTS area 716, an overlapping area 714, and an FDM light area 712. In the specific embodiment, the priority of the frequency domain is determined in the order of P1, P2, and P3 as shown in the figure. For example, in the case of full ADSL, the FDM 706 is the first priority of the allocation, the overlap area 708 has the second priority, and finally, if there is no other capacity, the POTS area 710 is used and the third area is used. Has priority.

By dynamically selecting and constructing various frequency modes, data can be efficiently allocated and communicated on the ADSL system. Furthermore, the priority scheme for allocating data for different areas is:
Useful for customizing a training sequence based on user input, channel characteristics or other desired parameters.

Referring to FIG. 10, an example of a method for allocating data will be described. At decision step 1002, the desired transmission data rate is compared to the available non-overlapping capacity. If the data rate exceeds the non-overlapping capacity, processing proceeds to step 1006, where the non-overlapping area is filled to capacity. Next, in this scenario, step 100
At 8, the remaining desired capacity is determined, which is equal to the desired data rate minus the non-overlapping capacity. Next, in step 1010, the remainder is assigned to the overlapping region of the frequency spectrum. However, if the data rate is less than or equal to the non-overlapping area, step 1
At 004, data rates are assigned only within non-overlapping regions. In this example method, the data capacity is assigned as a first priority a non-overlapping area (eg, FDM) before being assigned to an overlapping area (eg, upstream area).
Full area or FDM light area).
In this way, potential side effects due to overlapping areas, such as crosstalk and the absence of an echo cancellation device, are reduced.

Referring to FIG. 11, a specific method for allocating data to communication channels of a multi-carrier communication system is shown. In step 1102, the first transmitter TR1 receives the mode priority and area list. The priority and region lists may be fixed, determined from another transceiver via a message, or determined by a user, in which case they may be user-selectable.
Examples of the mode priority and area list include a non-overlapping area, an analog POTS area, and an overlapping area. The example priority scheme may have a non-overlapping area having priority over the overlapping area, and may have both non-overlapping and overlapping having priority using the analog POTS area. Next, in step 1104, TR1 sets the channel
Identify the channel characteristics of the communication channel, such as line length, noise, terrain or other user input. This particular channel characteristic may be measured, predetermined, or received from another transceiver or user. Next, in step 1106, the first transmitter TR constructs a training sequence for the channel based on the channel characteristics and based on the mode priority list. FIG. 12 shows a more specific method of implementing the training sequence. Finally, step 1
At 108, the training sequence is TR1
Transmitted on the channel. An advantage of the illustrated method of allocating data as shown in FIG. 11 is the flexibility in adapting to priority and channel characteristics. For example, by changing the training sequence for terrain, a system introduced into two different markets, for example the United States and Europe, will comply with two different industry conditions by selecting the training sequence according to terrain it can. Alternatively, if the training sequence is based on line length, different methods of training and data transmission can be employed depending on the particular length of the line between the transport device and the end user.

Referring to FIG. 12, a particular method for utilizing a channel length, such as a line length, to perform the construction of a training sequence is shown. First, step 12
At 02, the channel length of the communication channel is determined. One way to determine the line length is to measure the received power from the far-end transceiver and compare this received power to a predetermined power to line-length table. Furthermore, by averaging the received data,
Noise can be eliminated (factor out). Also, the line length may be received from an external source. In decision step 1204, the line length is compared to a threshold. This threshold may be a user input or may be predetermined.
Alternatively, it may be determined empirically. If the line length exceeds the threshold, a training sequence is constructed using the overlapping region of the frequency spectrum. However, if the line length does not exceed the threshold, at step 1206, a training sequence is constructed without utilizing the overlap region. In this method, the line length is used as a determination variable for determining when it is necessary to use the overlapping area when constructing a training sequence for subsequent data allocation and communication.

Referring to FIG. 13, another method of allocating data according to the line length will be described. In step 1302, a line length is determined. In step 1304, the line length is compared to a threshold. If the line length exceeds the threshold, the training
The sequence is constructed without using the high frequency domain. If the line length does not exceed the threshold, at step 1306, a training sequence is constructed to take advantage of the high frequency domain. For communication channels with long line lengths, it has been found that the high frequency region is not useful in gaining additional capacity, and by building a training sequence without utilizing such a high frequency region, The overall uplink and downlink system can be improved.

In this specification, a preferred method for improving the performance of an ADSL system has been identified. The invention has been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made to the present invention without departing from the scope of the invention as set forth in the claims below. For example, a particular embodiment has been described in terms of utilizing the SNRref table of FIG. 2 to determine bin loading. One skilled in the art will appreciate that other methods of determining bin loading are available. As another example, while the present disclosure has referred to ADSL, the methods, embodiments and systems set forth herein may be applied to other multi-carrier systems, including many other types of digital subscriber line (DSL) systems. Can also be applied. Accordingly, the invention is to be construed in accordance with the broadest possible interpretation as to the appended claims and their equivalents, rather than any of the specific embodiments described above.

[Brief description of the drawings]

FIG. 1 is a block diagram of an ADSL system.

FIG. 2 is a diagram of an SNR reference table.

FIG. 3 is a flow diagram illustrating a particular method for reducing power in a DMT system.

FIG. 4 is a flow diagram illustrating a particular method for reducing power in a DMT system.

FIG. 5 is a flowchart illustrating a specific method for reducing power of a DMT system.

FIG. 6 is a flowchart illustrating a particular method of allocating data.

FIG. 7 is a graph showing a frequency domain.

FIG. 8 is a flowchart illustrating a particular method of allocating data.

FIG. 9 is a flowchart illustrating a schematic method of data allocation in a redundant communication system.

FIG. 10 is a flowchart illustrating a specific example method for allocating data to different frequency domains.

FIG. 11 is a flowchart illustrating a specific method of allocating data for use by a transmitting transceiver.

FIG. 12 is a flowchart illustrating a communication system / data allocation method based on a line length.

FIG. 13 is a flowchart illustrating a second communication system / data allocation method based on a line length.

[Explanation of symbols]

 Reference Signs List 10 ADSL system 15 Transmission medium 20 Remote terminal 22, 34 System controller 24, 32 Transceiver 30 Central office

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kenneth Jay Cabanaus Grapevine Court 10801 in Austin, Texas, USA (72) Inventor Jeffrey P. Grayson Brighton Bend Lane, Cedar Park, Texas, USA 1417 (72) Inventor Peter Earl Molner West 37th Street, Austin, Texas, USA 1812

Claims (5)

[Claims] 1. Initiating the detection of characteristics of the communication channel; and a first mode in which the upstream data transmission and the downstream data transmission are transmitted in a frequency domain that does not substantially overlap; A second where the data transmission and the downstream data transmission are transmitted in substantially overlapping frequency domains
Utilizing the characteristics of the communication channel in a processing unit to establish a data transmission on the communication channel during one of the modes. 2. A method for allocating data for transmission on a communication channel, comprising: setting a desired communication rate for the communication channel; at least a first of the data for transmission on the communication channel. Assigning a portion to a non-overlapping frequency spectrum; and, if the non-overlapping frequency spectrum cannot handle the desired communication rate, assigning at least a second portion of the data to an overlapping frequency spectrum of the communication channel. A method comprising: 3. A method for constructing a communication channel of a digital multi-carrier overlapping telecommunications system, comprising: determining capacities for a plurality of different frequency regions of the communication channel; each of the capacities of the plurality of different frequency regions. Transmitting over the communication channel; and communicating data over the communication channel. 4. A processing unit for determining channel characteristics of a communication channel; a filter responsive to said processing unit;
And a line driver in communication with the communication channel; wherein the filter and the line driver communicate on a particular set of frequency domains of the communication channel in response to channel characteristics determined by the processing unit. The apparatus is dynamically constructed by the processing unit. 5. A computer readable device allocating data for transmission on a communication channel; setting a desired communication rate for said communication channel;
Assigning at least a first portion of the data to a non-overlapping frequency spectrum for transmission on the communication channel; and at least a second portion of the data if the non-overlapping frequency spectrum cannot cope with the desired communication rate. Computer-readable device characterized by at least one computer-executable routine.